Before her untimely death in 1897, the young French nun later canonized as St. Therese criticized the colorfully embroidered legends of the Catholic saints.

“We should not say improbable things,” wrote Therese, whose nickname was “The Little Flower.” “We must see their real, and not their imagined lives.”

St. Therese may have had a grip on reality, but the same can’t be said for Therese, the martyrlike Catholic patient awaiting death in a New Jersey hospital room in “The Little Flower of East Orange.”

Stephen Adly Guirgis’ dark, fascinating and surprisingly funny play gets a first-rate workout this month in its San Diego debut at Ion Theatre. Co-directed by Ion founders Glenn Paris and Claudio Raygoza, “Little Flower” ranks as one of the year’s best shows, particularly for the outstanding work of its excellent 10-member ensemble.

The 2008 play was inspired by Guirgis’ toxic relationship with his late mother, and since its debut, Guirgis had allowed only three theater companies to produce the deeply personal work. Ion is the fourth, and this well-designed, moving production surely would make him proud.

“Little Flower” is narrated by Danny (Guirgis’ alter-ego), an alcoholic and drug-abusing writer who ditches rehab (with his heroin-addicted fellow patient and girlfriend, Nadine) when he learns his wheelchair-bound, morphine-addicted mother Therese is in the hospital after what appears to be a failed suicide attempt.

Danny and Therese are co-dependents who love, loathe and can’t live without each other. To protect old family secrets, Therese has spun a web of lies that inescapably trap her and her children in a cycle of self-doubt, self-hatred and self-destructive behaviors.

The play’s great triumph is the naturalistic dialogue between mother and son — a biting give-and-take so honest it crackles with authenticity. And the scorching lava flow of resentment that erupts from Therese’s younger (and clearly less favored) child, Justina, is so real at times, it hurts.

As Danny, Jeffrey Jones is a marvel, so in the moment you’d swear his every word and reaction is spontaneously generated. Trina Kaplan’s bare-knuckles performance as Therese blends maternal love with passive-aggressive cruelty and delusion. And as Justina, Catalina Maynard is downright astonishing in her heartbreaking faceoff with a mother who never loved her nearly enough.

Other standout performances include that of San Diego newcomer Melinda Miller as the spacey but sweet druggie Nadine, Raygoza as the trash-talking male nurse Espinosa, and Paris as Halzig, a lost soul whose mother is dying in the next hospital bed.

The physical production is simple but evocative, particularly Melanie Chen’s haunting sound design and Raygoza’s projections of bleak and austere cityscapes.

Staging an edgy, very adult play with 10 actors in a 49-seat theater during the holidays would be financial suicide for most theaters, but Ion has a reputation for risk-taking that has brought it a loyal, theater-loving audience. “Little Flower” is raw — with rough language and some amusing sexuality — but it’s real, and it’s often very funny. It’s a powerful play, and it’s powerfully done at Ion Theatre.